Christopher M. Smemoe ,
Computer Science 450
Table of Contents 1. Using an Editor to Display the Image
2. Histogram of the Original Image
3. Using an Editor to Equalize the Image
4. Histogram Equalization of "mystery.pgm"
First, XV was used to display the image "mystery.pgm":
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As part of the program, the histogram of "mystery.pgm" was plotted.
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Next, the level operations built into XV were used to equalize the image. The result is displayed below:
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Next, I created a program that read in "mystery.pgm", computed the histogram, equalized the histogram, and output the equalized image.
The program can be downloaded here. The function "iiEqualizeImage" (which calls "iiComputeLookup") equalizes the image.
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Why is the resulting histogram non-uniform? The reason the Histogram after Equalization is not uniform is because of the finite number of gray levels in the original image. These gray levels are spread out and approximately equalized to produce the resulting histogram.
smemoe@byu.edu
Date last modified: 9/20/1999